Method for removing residual additives from elastomeric articles

ABSTRACT

A method for cleaning elastomeric articles comprising contacting the elastomeric article with at least one supercritical fluid under conditions and for a time sufficient to remove the phthalates and/or polynuclear aromatic hydrocarbons (PAHs) contained therein. Elastomeric articles having a reduced phthalte and/or PAH content prepared by the above method are also claimed. Such elastomeric articles having reduced phthalate contents can be utilized as gaskets, valves, seats, flaps or plugs in metered dose delivery devices such as aerosols for demanding medicinal and pharmaceutical uses.

The present application in the United States national applicationcorresponding to International Application No. PCT/US 92/10742, filedDec. 17, 1992 and designating the United States, which PCT applicationis in turn a continuation-in-part of U.S. application Ser. No.07/810,754, filed Dec. 18, 1991 now abandoned.

BACKGROUND

Certain elastomedc articles, i.e., gaskets, valves and seats used inaerosol containers, are designed as part of the container for theefficacious delivery of pharmaceutically active compounds, i.e.medicaments. As a matter of cost and convenience, such articles arederived using elastomedc materials such as elastomeric rubber and thelike, specifically formulated with ingredients that enable the articleto meet numerous demanding toxicological, chemical, and physicalrequirements. For example, gaskets and valves made of rubber aretypically formulated with about six to twelve ingredients, includingmonomers, polymers, organic solvents, organic plasticizers,antioxidants, antiozonants, curing agents, accelerators, pigments,tackifiers, reinforcing materials and inorganic fillers such as carbonblack. Nearly all cured or finished articles will inherently containsmall amounts of residual components derived from these ingredients.These inherent residual components or impurities are not neccessary forperformance of the article but can potentially interact with themedicament or other excipients in the formulation, leaciing to reducedpharmaceutical dosing. Such impurities could also interact with thecontainer, causing it to malfunction, such as by blocking a nozzleorifice.

A paper by A. Figazette et al., Analysis for Extractables From NitrileRubber Components in Metered Dose Inhalers, Pharmaceutical AnalysisDepartment, SmithKline Beecham Pharmaceuticals, King of Prussia, Pa.,was presented at the Symposium, "Regulatory Issues in Aerosol DrugDevelopment", June 12-14, 1991 in Arlington Va., by the University ofKentucky College of Pharmacy. Figazette et al stated that contaminationof pharmaceutical aerosols by substances leached from elastomedc valveassemblies in metered dose inhalers is a potentially serious problem.The authors present evidence that numerous extractables could bedetected in valves from various suppliers, demonstrating a need forcleaner valve rubbers with fewer leachable extractants. One class ofimpurities is known as the polynuclear aromatic hydrocarbons (PNAs orPAHs). Another class of impurities is known as non-PAHs, includingphthalates derived from plasticizers employed during processing.Presently, conventional methods for removing PAHs and non-PAHs fromrubber articles involves liquid-solid extraction and refluxing usingeither conventional solvents or fluorocarbon type solvents (eg. freons).However, these conventional method are deemed unsatisfactory forpreparing pudfied elastomedc articles using the newer, environmentallysafer fluorohydrocarbons propellants such as HFC-134A, HFC-226a andHFC-227, for the following reasons. First, these conventional methodshave the disadvantage of incurring high expenses for special handlingand safety precautions, and for special buildings, rooms and equipmentdue to the explosive nature of the newer propellants, necessitating theneed to use explosion-proof equipment. Second, these conventionalmethods have the further disadvantage of supedicially cleaning primarilythe outer surface of the article, leaving impurities in the intedor ofthe article.

Clearly, it would be desirable to provide an improved method forcleaning elastomedc articles by removal of the impurities containedtherein, particularly for highly demanding pharmaceutical and medicinaluses. It would also be desirable to provide a method for preparing sucharticles which would meet govenmental regulatory requirements (ie. Foodand Drug Administration). Furthermore, it would also be desirable toprovide a method for cleaning elastomeric articles that isoccupationally and environmentally safer, simpler, more rapid and lessexpensive than known conventional methods.

SUMMARY OF THE INVENTION

The present invention is directed towards a method for cleaningelastomeric articles comprising contacting the elastomeric article withat least one supercritical fluid under conditions and for a timesufficient to remove the phthalates and/or polynuclear aromatichydrocarbons (PAHs) contained therein. Selected phthalates includedibutyl phthalate or diisooctyl phthalate. Preferably the supercriticalfluid is carbon dioxide.

The present invention is also directed toward an elastomeric articlehaving a reduced phthalate and/or PAH content prepared by the abovemethod. Preferably the elastomedc article is made of rubber, preferablynitrile rubber. Also preferred is that the elastomeric article is arubber gasket, valve, seat, flap or plug, such as those employed inmetered dose delivery devices, which use chlorofluorohydrocarbons orfluorohydrocarbons as propellants. The propellant can be achlorofluorohydrocarbon such as PDP-11 or a fluorohydrocarbon such asHFC-134A, HFC-226A or HFC-227.

One advantage of the present invention is that it provides an elastomedcarticle for medicinal or pharmaceutical use whose phthalate and/or PAHcontent is significantly lower than similar articles cleaned byconventional procedures.

A second advantage of the present invention is that it provides asimpler and faster method for removing phthalate and/or PAH impuritiesfrom an elastomedc article, compared to conventional procedures.

A third advantage of the present invention is that it provides a methodfor removing phthalate and/or PAH impurities from elastomedric articlesthat is less expensive than by other known procedures.

A fourth advantage of the present invention is that it provides anoccupationally and environmentally safer method for removing phthalateand/or PAH impurities from elastomedc articles, compared to conventionalprocedures.

DETAILED DESCRIPTION OF THE INVENTION

Throughout the specification, the terms "purifying" and "cleaning" areused interchangeably.

As defined by Gessner G. Hawley, The Condensed Chemical Dictionary,10the Edition, Van Nostrend Reinhold Co., New York, (1981 ), 1135 pp.,the term "elastomer" as originally defined by Fisher (1940), refers tosynthetic thermosetting high polymers having properties similar to thoseof vulcanized natural rubber, namely, the ability to be stretched to atleast twice their original length and to retract very rapidly toapproximately their original length when released. Among the betterknown elastomers are styrene-butadiene copolymer, polychloroprene(neoprene), nitrile rubber, butyl rubbers such as the non-halogenatedrubbers, the chlorinated rubbers and brominated rubbers; polysulfiderubber ("Thiokol"), cis-1,4-polyisoprene, ethylene-propylene terpolymers(EPDM rubber), silicone rubber and polyurethane rubber. These can becross-linked with sulfur, peroxides or similar agents. The term alsoincludes uncross-linked polyolefins that are thermoplastic, generallyknown as TPO rubbers. Their extension and retraction properties arenotably different from those of thermosetting elastomers, but they arewell adapted to specific uses such as specialized mechanical products.

Also as defined by The Condensed Chemical Dictionary, above, the term"rubber" refers to any of a number of natural or synthetic high polymershaving unique properties of deformation (elongation or yield understress) and elastic recovery after vulcanization with sulfur or othercross-linking agent, which in effect changes the polymer fromthermoplastic to thermosetting. The yield or stretch of the vulcanizedmaterial ranges from a few hundred to over 1000 per cent. Thedeformation after break, called "permanent set" is usually taken as theindex of recovery. It ranges from 5 to 10% for natural rubber to 50% ormore for some synthetic elastomers, and varies considerably with thestate of vulcanization and the pigment loading. Representative rubbersinclude nitrile rubbers or neoprene, GR-S rubbers, polyisoprene,polybutadienes, and polysiloxanes.

The term "propellants" refers to both compressible and incompressiblegases used to expel the contents of containers in the form of aerosols,and include freons, fluorohydrocarbons, hydrocarbon gases such as butaneand propane, carbon dioxide (CO₂), nitrogen (N₂), oxygen (O₂) andnitrous oxide (N₂ O).

Such elastomeric materials can be useful for preparing articles formedical or pharmaceutical use such as rubber gaskets, valves, seats,flaps, stoppers and plugs used in aerosol containers, atomizers, pumpsprays, droppers and other metered dose devices. Another use for suchmaterials would be for stoppers used to cap vials, bottles, infusionbags, syringes, blood collection tubes and parenteral containers. Andyet another use for such materials would be for septa used in analyticalequipment such as injection ports of gas chromatographs. Otherelastomeric materials include those used for implantation devices suchas heart valves, limb joints, breast implants, intravenous andintestinal tubing, dental retainers and pharmaceutical containers.Another application could be for devices which are contacted with themouth such as baby nipple, toothpicks, mouthguards used in sports, scubadiving mouthpieces, feed tubes, tracheal tubes and thermometers.

An apparatus for supercritical extraction is made up of an extractioncell, preferably cylindrical, which is housed in a chamber forcontrolling temperatures and pressures. At least one supercritical fluid(ie. extracting mobile phase), such as CO₂, is pumped into theextraction cell, through a pressure regulating restrictor to maintainback pressure and into a vessel which serves as a trap. As thesupercritical fluid passes through the elastomeric article containingphthalate and/or PAH impurities, the supercritical fluid removes thephthalate and/or PAH impurities from the elastomeric article, leavingbehind an elastomeric article whose phthalate and/or PAH content issignificantly reduced. As the supercritical fluids containing thephthalate and/or PAH impurities leave the chamber, the fluids transforminto a gas, which can be passed through or injected (ie. bubbled) into atrapping vessel.

The use of supercritical fluid extraction for analytical purposes isknown. For example, in Supercritical Fluid Extraction andChromatography, edited by Bonnie A. Charpentier and Michael R.Sevenants, ACS Symposium Series 366, by B. Wright et al., in Chapter 3:"Analytical Supercritical Fluid Extraction Methodologies" (1988), theauthors teach that several polycyclic aromatic hydrocarbons (PAHs) wereextracted from a chromatographic resin, ie. XAD-2, superficially spikedwith several PAHs, using carbon dioxide at 325 bar and 50° C. for 7minutes. However, this reference fails to describe a process forremoving phthalate and/or PAH impurities from an elastomeric articlewhose phthalates and/or PAHs have been integrated throughout the 10entire matrix of the elastomer article as a result of mixing, heatingand curing steps involved in preparation of the elastomeric article.

The elastomedc article can be contacted with at least one supercriticalfluid under conditions effective to extract phthalates and/or PAHimpurities from the elastomeric article. The contacting of the articlewith the supercritical fluid can be carried out at temperatures rangingfrom about ambient to below the temperature resulting in degradation ofthe elastomer, such as from about 25° C. to about 300° C., preferablyfrom about 25° C. to about 50° C., more preferably from about 30° to 35°C. The pressure at which the article can be contacted with thesupercritical fluid can range from about 50 atmospheres (atm) to about400 atm, preferably from about 100 to about 400 atm. The elastomericarticle should be contacted with at least one supercritical fluid for atime sufficient to reduce the phthalate and/or PAH impurities to thedesired level. Preferably the contacting is carried out for greater thanone hour, more preferably for greater than two hours, most preferablyabout 4 hours or more. Generally, the longer contacting times with thesupercritical fluid(s) allows for higher extraction of phthalates and/orPAHs.

The supercritical fluid employed in the present process can be one ormore of any of those described in U.S. Pat. No. 4,749,522.Representative extracting (solvating) mobile phase components includethe elemental gases such as helium, argon, nitrogen and the like;inorganic compounds such aS ammonia, carbon dioxide, nitrous oxide,water, and the like; and organic compounds. Suitable organic compoundsinclude C-1 to C-5 alkanes such as propane and butane; alkyi halidessuch as monofluoromethane, carbon tetrachloride, chloroform, methylenechloride; aromatics such as xylene, toluene and benzene; aliphatics suchas C-5 to C-20 alkanes including hexane, heptane and octane; C-1 to C-10alcohols such as methanol, ethanol, propanol, butanol and isopropanol;ethers or acetone. Where more than one supercritical fluid is employed,the supercritical fluid employed in the larger amount, ie. greater than50% on a volume basis, is considered to be the main solvent. If three ormore supercritical fluids are employed, the main solvent will be thatmaking up the largest proportion in the mixture. Co-solventsupercritical fluids which can supplement and tend to modify thesolvating properties of the main supercritical fluid are employed inlower amounts relative to the main supercritical fluid, generally fromabout one to less than 50% on a volume basis, preferably from about oneto about 10% relative to the main supercritical fluid. The co-solventsupercritical fluid employed in the present process should be compatiblewith the main supercritical fluid and also be capable of at leastpartially dissolving some of the impurities being extracted. Suitableco-solvents for use in conjunction with the supercritical fluid includeany of those cited above for the main supercritical fluid or mixturesthereof.

One representative method for determining the phthalate and/or PAHcontent of an article cleaned by the present process is as follows. Theelastomeric article to be tested is immersed or refluxed for a certainperiod of time with a solvent or solution matched for the environment inwhich the elastomeric article will be used. For example, elastomericgaskets and seals used in aerosols can be immersed for about one tothree weeks in an aerosol propellant, such as Freon11, Freon12, HFC134A,HFC-226A or HFC-227. After the immersion period, the amount ofphthalates and/or PAHs in the resultant solution (ie. propellant orresidue thereof) is determined. Generally, the fewer phthalates and/orPAHs found in the resultant solution, the purer or "cleaner" is theelastomedc article. Similarly, the greater the amount of phthalatesand/or PAHs found in the resulting solution corresponds to a highercontent of phthalate and/or PAH impurities in the elastomeric article.

Phthalates impurities which can be extracted from an elastomeric articleinclude those of the formula C₆ H₄ (COOR)₂ wherein R represents C-1 toC-12 alkyl such as such as for example methyl, ethyl, propyl, isopropyl,butyl, isobutyl, tert-butyl, pentyl, hexyl, octyl, isooctyl, decyl andthe like. Other non-PAH impurities which can also be removed with thepresent process include 2-mercaptobenzothiazole (2-MCBT),N-cyclohexyl-2-benzthiazyl sulphenamide (CBS), nitrosamines, residualoligomers and certain plasticizers such as waxes, esters, stearates andphthalates such as dioctyl phtalate.

PAH impurities which can be extracted from an elastomeric article withthe present process include those designated in U.S. EnvironmentalProtection Agency Method 8310 - Polynuclear Aromatic Hydrocarbons, pp8310-1 to 8310-13: acenaphthene, acenaphthylene, anthracene,benzo(a)anthracene, benzo(a)pyrene, benzo(b)pyrene, benzo(e)pyrene,benzo(b)fluoranthene, benzo(ghi)perylene, chrysene,benzo(k)fluoranthene, dibenz(a,h)acridine, dibenz(a,j)acridine,dibenzo(a,h)anthracene, dibenzo(c,g)carbazole, dibenzo(a,e)pyrene,dibenzo(a,h)pyrene, dibenzo(a,i)pyrene, fluoranthene, fluorene,indeno(1, 2, 3-cd)pyrene, 3-methylcholanthrene, naphthalene, perylene,phenanthrene, pyrene or triphenylene.

After the immersion period is completed, impurities in the resultantsolution can be analyzed using conventional analytical procedures, suchas liquid chromatography, capillary chromatography, gas chromatography,and the like. Representative procedures to analyze for impurities in theresultant solution are provided below. Other analytical procedures suchas supercritical fluid extraction (SFE) can be employed to analyze thesolvent or propellant, especially where a particular impudty cannot besatisfactorily detected by conventional procedures. Analytical ProcedureNo. 1. Analysis for Phthalates

A pressurized aerosol can is cooled in a freezer for one hour. The freonpropellant contained therein is slowly vented from each can via a slowincision made at the top of the can. Following the complete removal ofthe freon propellant, the valve assembly is removed and discarded. Eachcan is then dnsed with one milliliter (mL) of dichloromethane containing7.3 mg/mL of N-tetradecane, which serves as a volume indicator (ie.internal standard). The resultant dichlormethane extract is theninjected into and analyzed using a gas-chromatographic/massspectroscopic system. Analytical Procedure No. 2. Liquid chromatographywith Fluorescence Detection for Analyzing PAH.

This Food and Drug Administration (FDA) validated procedure uses a flowinjection analysis. (FIA) system made of a high performance liquidchromatography pump, an auto-injector, a fluorescence detector (filteror monochromator) set at the absorption maximum of anthracene at 250nanometers (nm) and emission maximum at 397 nm, or use Kodak Wrattanfilters No. 30, 34 or 39 or equivalent as emission filters, and chartrecorder. The mobile phase is acetonitdle set at a flow rate of onemilliliter per minute. A series of standards ranging from aconcentration of 5 paRRs per billion (ppb) to 500 ppb is prepared usinganthracene in acetonitrile. From the standards, a response curve isdetermined by plotting the response generated by the fluorescencedetector versus varying concentrations of the anthracene standards. Thesample, pressurized aerosol can is cooled in a dry ice/methanol bath andthe top of the can is removed. The contents of the can and rinses of thevalve assembly and empty can are filtered into a volumetric flask. Afterthe propellant has evaporated, the volumetric flask is diluted to volumewith acetonitrile or methylene chloride. The resulting solution isanalyzed on the FIA for anthracene and the results are quantitativelymeasured by comparison with the standard response curve. AnalyticalProcedure No. 3. Gas chromatography for Analyzing PAHs.

This Environmental Protection Agency (EPA) procedure uses a system madeof a PTE-5 QTM fused silica capillary column having dimensions of 15meters (m) by 0.53 millimeters (mm) internal diameter (I.D.) and a flameionization detector (FID). Helium is used as the carder gas at a fl0wrate of 10 mL per minute. A series of 19 standards are prepared, eachstandard containing a specific PAH in methylene chloride in aconcentration of 1.2 nanograms (ng) per microliter (μL). The columntemperature is increased to 85° C. and held at this temperature for fourminutes; then increased at a rate of 15° C. per minute to 300° C. andheld for two minutes. The sample, pressurized aerosol can is cooled in adry ice/methanol bath and the top of the can is removed. The contents ofthe can and rinses of the valve assembly and empty can are filtered intoa volumetric flask. After the propellent has evaporated, the volumetricflask is diluted to volume with acetonitrile or methylene chloride. Theresultant solution is analyzed on the gas chromatograph for the presenceof any of the 19 PAHs.

It is highly desirable that the integrity of the article being cleanedof phthalates and/or PAHs is maintained. Thus, the present invention isnot directed toward cleaning articles whose utility would be destroyedby exposure to supercritical fluids. For example, exposing a patchcontaining an adhesive to supercritical fluids would render the patchineffective by dissolving or removing the adhesive.

In addition to removing phthalates and/or impurities, the present methodhas the advantage of providing an elastomeric article having aSignificantly reduced phthalate and/or PAH content whose physicalproperties are still maintained. Maintaining and verifying the retentionof certain physical properties following cleaning is useful to assureproper mechanical functioning of the article. For example, a gasket orvalve component can be evaluated for durometer (ie. hardness), tensilestrength and elongation or compression set. Hardness can be evaluatedwith any suitable hardness tester with the desired sensitivity, usingprocedures such as described in ASTM-D-1415∝68, Part - 68, July 1973 -International Hardness of Vulcanized Rubber or ASTM D-2240-75. Tensilestrength and elongation can be evaluated with any suitable tensometerand extensometer, using procedures such as ASTM D-412-75. Compressionset can be evaluated with any suitable compression set device, usingprocedures as described in ASTM D395-78.

EXAMPLE - Cleaning of Rubber Valve Components for Aerosols: Removal ofPhthalates and PAHs

a) Supercritical Fluid Cleaning Using CO₂

To a ten mL stainless steel extraction cell is added one gram of nitrilerubber valve components. The operating conditions for supercriticalcleaning are as follows:

    ______________________________________                                        Head Space Filler:                                                                             Helium                                                       Restrictor Flow: 500 mL/min                                                   Extracting Mobile Phase                                                                        Supercritical fluid grade CO.sub.2                           (ie. supercritical fluid):                                                    Oven Temperature:                                                                              35° C.                                                Pressure Program:                                                                              a. 100 atm. for 2 minutes                                                     b. 200 atm. for 2 minutes                                                     c. 225 atm. for 2 minutes                                                     d. 250 atm. for 2 minutes                                                     e. 275 atm. for 2 minutes                                                     f. 300 atm. for 240 minutes                                  Total Extraction Time:                                                                         1, 2 or 4 hours                                              ______________________________________                                    

b) Measuring Phthalates and Other Impurities

Various groups of nitdie rubber valve components are tested forphthalates impurities. One group of valve components represents thecontrol, which receives no cleaning after manufacture of the valvecomponent. A second group of valve components is cleaned conventionallyby refluxing the valve components in Freon P11 for 72 hours, followed byair drying. A third group of valve components is cleaned using themethod of a) Supercritical Fluid Cleaning Using CO.sub., above. Eachgroup of nitrile rubber valve components is placed into a 10 mL aerosolcontainer and immersed in 15 g of Freon 11. The containers are sealedand maintained at 40° C. for two weeks. The containers are opened andthe Freon is evaporated. The chemical residue in the container isanalyzed for phthalates impurities by a suitable analytical procedure.

                  TABLE I                                                         ______________________________________                                        Assay of Impurities Found in Extracts From                                    Unprocessed Rubber, Conventionally Cleaned Rubber                             and Supercritical Fluid (SFE) Cleaned Rubber Used                             for Aerosol Seals and Gaskets                                                            μg in extract                                                                          Conven-                                                             Un-       tionally SFE-                                                       processed Cleaned  Cleaned Rubber                                Extracted Impurity                                                                         Rubber    Rubber   1 hrs                                                                              2 hrs                                                                              4 hrs                               ______________________________________                                        Cyclohexyl   7         <0.1     26   1    0.1                                 Isothiocyanate                                                                2,6-Di-t-butyl-4-                                                                          <0.1      <0.2     <0.1 0.2  <0.1                                methylpheno                                                                   2-Cyanoethyldimethyl-                                                                      67        0.1      71   4    0.2                                 dithiocarbamate                                                               Dibutyl phthalate                                                                          8         0.7      6    <0.1 0.1                                 2,2-Methylene-bis-(4-                                                                      6         7        3    12   6                                   methyl-                                                                       tert-butyl phenol)                                                            Octadecanoic Acid                                                                          22        11       27   12   3                                   Carbamodithioic Acid                                                                       2         <0.1     <0.1 <0.1 <0.1                                Ester.sup.a                                                                   Unknown A    7         <0.1     0.4  <0.1 <0.1                                Unknown B    2         <0.1     1    <0.1 <0.1                                Unknown C    16        2        9    2    0.3                                 Unknown D    7         11       2    47   0.8                                 Diisoctyl Phthalate                                                                        28        9        6    3    0.1                                 High boiling aliphatics                                                                    11        2        4    6    2                                   Total mg Detected                                                                          183       43       155.4                                                                              87.2 19.8                                ______________________________________                                    

The results in Table 1 demonstrate that of the three rubbers tested, the4-hour SFE-cleaned rubber had the lowest amounts of extractableimpurities (ie. 19.8 rag) compared with the unprocessed (183 rag) andconventionally cleaned rubbers (43 mg). Also, the 4-hour SFE-cleanedrubbers had the lowest amounts of phthalates. For example, rubbers haddibutylphthalate and diisooctyl phthalate amounts which were 7- and90-fold lower, respectively, than the rubbers conventionally cleanedusing solvent extraction with Freon 11.

                  TABLE II                                                        ______________________________________                                        Physical Properties of Supercritical Fluid (SFE) Cleaned                      Rubber Prepared from Unprocessed Rubber Used                                  for Aerosol Seals and Gaskets                                                                                Change in                                                  Change in                                                                             Change in  Physical                                                   Weight  Hardness   Properties                                     ______________________________________                                        Unprocessed Rubber                                                                          No change No change  No change                                  4 hr SFE-Cleaned                                                                            -4.00 mg  No change  No change                                  Rubber                                                                        2 hr SFE-Cleaned                                                                            -3.13 mg  No change  No change                                  Rubber                                                                        1 hr SFE-Cleaned                                                                            -2.29 mg  No change  No change                                  Rubber                                                                        ______________________________________                                    

The results in Table II demonstrate that the SFE-cleaned rubbersincurred a loss in weight, reflecting a significant loss of impuritiesfrom the rubber matrix. However, despite this significant weight loss,no change for either hardness or the physical proprieties of theSFE-cleaned rubbers was observed.

                  TABLE III                                                       ______________________________________                                        Assay of Impurities: Non-Volatile Residues and                                Total Polynuclear Aromatic Hydrocarbon Content (Per                           Anthracene Equivalents) Found in Extracts From                                Unprocessed Rubber, Conventionally Cleaned Rubber Used                        for Aerosol Seals and Gaskets                                                             Non-Volatile                                                                  Residues    PAH Content                                                       (Peak Area  (ppb of PAHs/mg                                                   Counts/mg rubber)                                                                         Rubber)                                               ______________________________________                                        Unprocessed Ruber                                                                           2024          10                                                Conventional Cleaning                                                                       747           7                                                 4 hr SFE-Cleaned                                                                            458           3                                                 Rubber                                                                        2 hr SFE-Cleaned                                                                            1443          15                                                Rubber                                                                        1 hr SFE-Cleaned                                                                            13,774        13                                                Rubber                                                                        ______________________________________                                    

The results in Table III demonstrate that the 4 hour SFE-cleaned rubbershad the lowest total polynuclear aromatic hydrocarbon content (ie. 3ppb/mg rubber) as compared to either the unprocessed rubber (ie. 7ppb/mg rubber) or the conventionally cleaned rubbers (10 ppb/mg rubber).Similarly, the 4 hour SFE-cleaned rubbers had the lowest nonvolatileresidues (ie. 458 area counts/mg rubber) of all the rubbers tested.

We claim:
 1. A cleaned vulcanized elastomeric article made of nitrilerubber wherein prior to cleaning the vulcanized elastomeric articlecontained phthalate and/or PAH impurities integrated throughout itsmatrix, wherein the the cleaned vulcanized elastomeric article has alower phthalate and/or PAH impurity content than a comparable vulcanizedelastomeric article cleaned conventionally by refluxing in Freon P11 for72 hours, wherein the cleaned vulcanized elastomeric article is preparedby contacting the vulcanized elastomer with at least one supercriticalfluid until the content of phthalate and/or polynuclear aromatichydrocarbon (PAH) impurities contained therein is lower than that of acomparable article cleaned conventionally.
 2. A cleaned vulcanizedelastomeric article which is a rubber gasket, valve, seat, flap, stopperor plug in a metered dose delivery device, wherein prior to cleaning,the vulcanized elastomeric article contained phthalate and/or PAHimpurities integrated throughout its matrix wherein the cleanedvulcanized elastomeric article has a lower phthalate and/or PAH impuritycontent than a comparable vulcanized elastomeric article cleanedconventionally by refluxing in Freon P11 for 72 hours, wherein thecleaned vulcanized elastomeric article is prepared by contacting thevulcanized elastomer with at least one supercritical fluid until thecontent of phthalate and/or polynuclear aromatic hydrocarbon (PAH)impurities contained therein is lower than that of a comparable articlecleaned conventionally.
 3. A cleaned vulcanized elastomeric articlewhich is a rubber gasket, valve, seat, flap, stopper or plug in anaerosol container containing chlorofluorohydrocarbons orfluorohydrocarbon propellants, wherein prior to cleaning, the vulcanizedelastomeric article contained, phthalate and/or PAH impuritiesintegrated throughout its matrix, wherein the cleaned vulcanizedelastomeric article has a lower phthalate and/or PAH impurity contentthan a comparable vulcanized elastomeric article cleaned conventionallyby refuxing in Freon P 11for 72 hours, wherein the cleaned vulcanizedelastomeric article is prepared by contacting the vulcanized elastomerwith at least one supercritical fluid until the content of phthalateand/or polynuclear aromatic hydrocarbon (PAH) impurities containedtherein is lower than that of a comparable article cleanedconventionally.
 4. A cleaned vulcanized elastomeric article having alower phthalate and/or polynuclear aromatic hydrocarbon (PAH) impuritycontent than a comparable vulcanized elastomeric article cleanedconventionally by refluxing in Freon P11 for 72 hours, wherein prior tocleaning the vulcanized elastomeric article contained phthalate and/OrPAH impurities integrated throughout its matrix, and the cleanedvulcanized article is prepared by contacting the vulcanized elastomerwith at least one supercritical fluid until the content of phthalateand/or polynuclear aromatic hydrocarbon (PAH) impurities containedtherein is lower than that of a comparable article cleanedconventionally.
 5. A cleaned vulcanized elastomeric article made ofnitrile rubber wherein prior to cleaning, the vulcanized elastomericarticle contained phthalate and/or PAH impurities integrated throughoutits matrix, wherein the cleaned vulcanized elastomeric article has alower phthalate and/or PAH impurity content than a comparable vulcanizedelastomeric article cleaned conventionally by refluxing in Freon P11 for72 hours.
 6. A cleaned vulcanized elastomeric article which is a rubbergasket, valve. seat, flap. stopper or plug in a metered dose deliverydevice, wherein prior to cleaning, the vulcanized elastomeric articlecontained phthalate and/or PAH impurities integrated throughout itsmatrix, wherein the cleaned vulcanized elastomeric article has a lowerphthalate and/or PAH impurity content than a comparable vulcanizedelastomeric article cleaned conventionally by refluxing in Freon P11 for72 hours.
 7. A cleaned vulcanized elastomeric article which is a rubbergasket. valve. seat, flap, stopper or plug in an aerosol containercontaining chlorofluorohydrocarbons or fluorohydrocarbon propellants,wherein prior to cleaning, the vulcanized elastomeric article containedphthalate and/or PAH impurities integrated throughout its matrix,wherein the cleaned vulcanized elastomeric article has a lower phthalateand/or PAH impurity content than a comparable vulcanized elastomericarticle cleaned conventionally by refluxing in Freon P11 for 72 hours.8. A cleaned vulcanized elastomeric article having a lower phthalateand/or polynuclear aromatic hydrocarbon (PAH) impurity content than acomparable vulcanized elastomeric article cleaned conventionally byrefluxing in Freon P11 for 72 hours, wherein prior to cleaning, thevulcanized elastomeric article contained phthalate and/or PAH impuritiesintegrated throughout its matrix.